The rapid development of the mobile Internet and the Internet of Things has provoked an explosive growth of data traffic and the extensive emergence of diversified and differentiated services. 5G as a new generation of mobile communication technology, compared with 4G will support a higher rate (such as Gbps), massive link (such as 1M/Km2), ultra-low latency (such as 1 ms), higher reliability, and hundredfold energy efficiency improvement to support the new requirement changes. Among them, the ultra-low latency, as a key index of 5G technology, directly affects the development of latency-limited services such as the Internet of Vehicles, industrial automation, remote control, smart grid, etc. At present, researches on a series of standards on reducing 5G latency are gradually being pushed forward.
The Transmission Time Interval (TTI) reduction, as an important research direction for reducing the current latency, aims to reduce the current TTI length of 1 ms to 0.5 ms or even to a length of 1-2 Orthogonal Frequency Division Multiplexing (OFDM) symbols, which can multifoldly reduce the minimum scheduling time, thereby multifoldly reducing the single transmission latency without changing the frame structure. How to design an effective transmission method to reduce transmission latency is a problem that needs to be solved.